The present invention relates to a programmable electronic calculator and, more particularly, to a portable, programmable electronic calculator or a portable, personal computer.
The conventional electronic calculators have a one-line display device composed of a liquid crystal display to match a limited display zone. In such a narrow display device, previous display contents must be removed from the narrow display device to show recent display contents. It is impossible to simultaneously display a plurality of items of data.
However, in a particular mode for the electronic calculator such as a program debug mode, it is indispensable to display the plurality of items including program lines of the program to be run, the serial number of the lines, and the calculated results etc. Since it was impossible to simultaneously display the plurality of items, the program debugging operation were not effectively achieved.
In another aspect of the electronic calculator, it has been proposed to provide a specific type of electronic calculator for enabling a reserve mode wherein a specific function key sequence (key operation sequence) can be assigned to any one of several reserve keys. It is very easy to define a specific function of a single one of the reserve keys provides the same effect as if a plurality of keys are operated. Any desired key sequence can be reserved independently of the number of the key switches installed.
The reserve mode is different from a double function mode in which a specific function is defined by subsequently actuating a function group selecting key and a specific function key. In the double function mode, all the functions must be printed near the related key switches. The kinds of functions stored may depend on the number of key switches installed.
In the electronic calculator for enabling the reserve mode, it is very inconvenient to determine the key sequences which have been reserved, in particular, when the number of the reserve keys is great.